The invention is based on a sieving device with at least one rotary drum unit comprising a plurality of sieving openings, said sieving openings being respectively arranged around a centre point of the sieving openings and being categorized in at least one structure group and at least one further structure group and at least one further structure group, wherein the first structure group the centre points of neighbouring sieving openings are arranged at a first intra-distance to one another, and wherein in the further structure group the centre points of neighbouring sieving openings are arranged at a further intra-distance to one another, wherein the smallest structure distance between a centre point of at least one sieving opening in the at least one first structure group and a nearest situated center point of at least one sieving opening in the at least one further structure group is greater than the first intra-distance.